In the semiconductor industry, chemical-mechanical polishing (CMP) is used to remove a portion of a film deposited on a wafer. With CMP, a film is selectively removed from a semiconductor wafer by rotating the wafer against a polishing pad (or rotating the pad against the wafer, or both) with a controlled amount of pressure in the presence of a slurry. Monitoring and controlling the CMP process is difficult; such tasks including but not limited to (1) detecting when polishing should be stopped (i.e. the endpoint has been reached), (2) detecting particles in the slurry which cause scratching, (3) detecting chemical species for contamination control, or (4) understanding process chemistry, would all be desirable.
Such tasks as (1), (3), and (4) could be achieved by in-situ real time (i.e. while the wafer is being polished) slurry sampling and analysis of gaseous reaction products resulting from a reaction between the slurry and the layer(s) being polished on the wafer. However, a robust collection apparatus is needed, which is not affected by the slurry chemistry, does not interfere with the polishing, and enables sampling with a rapid response time.